The 3rd Generation Partnership Project (3GPP) decided to establish a standard for Mission Critical Push-to-Talk (MCPTT) Communications over Long-Term Evolution (LTE) (for Release 13). MCPTT systems utilized by public safety (PS) agencies enable their personnel to selectively and sequentially transmit messages to one another, either on a one-to-one or one-to-many basis over LTE. MCPTT service domain is usually operated by an entity (PS agency) different from the entity operating LTE and IP Multimedia Subsystem (IMS) domain. In such cases, each domain may have to provide their own identity and execute their own security mechanisms to ensure authenticity and privacy of the PS users, while adhering to stringent call setup time requirements.
There are significant efforts in considering a Session Initiation Protocol (SIP) Core based Architecture for the MCPTT Applications. In the IMS, authentication of the subscriber is performed during the registration procedures. Currently defined IMS/SIP registration procedures includes single authentication to complete the IP-based service registration procedure. The application level registration is performed using third party registration, and after IP connectivity for the signaling has been gained from the access network. In case if a separate application level authentication is needed, then currently there is no solution available in the IMS specifications.
For MCPTT service, it is required to perform separate authentication in addition to the IMS authentication. This is due to isolation of MCPTT credentials from the SIP core credentials and due to different service providers.
Further, in some scenarios it is required to have multiple authentications to register for the IP-based service. Especially, when the IMS is owned by the mobile operator and MCPTT service is owned by public safety agency. Considering the following illustrative scenarios, where the PS agency or the Mobile network Operator (LTE) Administrates MCPTT System and/or SIP core:
In some cases, if the MCPTT capable UE is shared (sharable UE). The sharable MCPTT UE is a pool of UE's wherein each UE being interchangeable with any other, and users randomly choosing one or more UE's from the pool of UE's, each user for temporary exclusive use. The shareable MCPTT UE can be used by the user who can gain access to the MCPTT client application stored therein and can become an authenticated MCPTT user.
Based on the MCPTT security requirements and scenarios, multiple authentications (IP-based service access level and also application level (MCPTT) within the registration process needs to be performed.
Thus, there is a need of a simple and robust mechanism for performing multiple (IMS and MCPTT) authentications within the single SIP registration process. Especially for the scenarios, where application layer signaling network for session initiation/control/management and the application server are administrated by different providers/operators.
The above information is presented as background information only to help the reader to understand the present invention. Applicants have made no determination and make no assertion as to whether any of the above might be applicable as Prior Art with regard to the present application.